Expand your home’s potential with our ADU services, perfect for guest houses, rental units, or extended family living spaces. We handle all aspects from design and permitting to construction and finishing.
Home Additions and ADUs in San Diego
At some point most families face the same question: move, or build. Moving means a new mortgage, a new neighbourhood and the whole cost of transacting. Building means keeping the street you chose, the school you like and the equity you have, and making the house fit the life you actually have now.
Seven Home Improvement designs and builds both attached additions and accessory dwelling units across San Diego County. One licensed team from feasibility through final inspection. CSLB #1078564.
Additions or ADUs: Which One Do You Need?
The two get discussed interchangeably and they are not the same thing.
A home addition extends your existing house. A new bedroom, a primary suite, a larger kitchen and living area, or a second storey. It shares your walls, your systems and your front door, and it becomes part of the same dwelling.
An ADU is a separate, self-contained home on your lot with its own entrance, kitchen and bathroom. It can be detached, attached to the main house, or converted from an existing garage. Because it is a legally separate dwelling, it can be rented, occupied by family, or used to house an aging parent independently.
The right answer usually comes down to what the space is for. If you need more room in your household, that is an addition. If you need a second household on the property, that is an ADU. We work through it with you at the feasibility stage, and we price both options when it is genuinely a toss-up.
Home Additions
Additions we build regularly:
- Bedroom and bathroom additions
- Primary suite additions with walk-in closet and en-suite
- Kitchen and living area expansions
- Second-storey additions
- Bump-outs that widen an existing room
- Garage additions and conversions
Additions start from $250 per square foot, and construction typically runs 3 to 5 months. Design, engineering and permitting happen before construction begins and run on their own schedule.
ADUs and Junior ADUs
We build four kinds, and the difference between them is mostly how much new structure is involved:
- Junior ADU (JADU), up to 500 sq ft: from $50,000. Created within the existing footprint of the home, typically by converting a bedroom and adding an efficiency kitchen and its own entrance. The lowest-cost route to a legal second unit.
- Garage conversion: from $80,000. Converts an existing garage into a full dwelling. The structure and slab already exist, so cost and schedule come down.
- Attached ADU: from $150,000. New construction attached to the main house, sharing one wall but with its own entrance and services.
- Detached ADU: from $250,000. A standalone building on the lot. The most flexible layout and the strongest privacy for both households.
Every project is scoped and quoted individually. City permits and fees are billed separately.
An ADU typically takes 10 to 14 months end to end, including design, engineering, permitting and construction. That figure is the honest one. Permitting is a meaningful share of it and is largely outside any builder’s control. Be cautious of anyone quoting an ADU schedule that counts construction only.
Ground-Up and New Construction
We also build complete homes from the ground up, from $300 per square foot. Construction runs 8 to 12 months, and 18 to 24 months end to end including design, engineering and permitting.
Every project is scoped and quoted individually. City permits and fees are billed separately.
Why Homeowners in San Diego Build ADUs
Three reasons come up in nearly every consultation.
Rental income. A legal second unit on a lot you already own generates income without buying more land.
Multigenerational living. An ADU lets an aging parent or an adult child live independently on the same property: close enough to help, separate enough that everyone keeps their own front door.
Property value. A permitted, legal dwelling is a permanent addition to what the property is, not a cosmetic upgrade.
What Determines the Cost of an ADU
Two ADUs of the same size on two different lots can price very differently, and the reasons are almost always the same handful of things. Knowing them early is what stops a project stalling at the design stage.
- Whether you are converting existing structure or building new. A garage conversion starts with a slab, walls and a roof already paid for. A detached build starts with none of it.
- Utility runs. How far the new unit sits from existing water, sewer and electrical service, and whether the main panel has the capacity for a second dwelling. A long trench across a finished yard is real money.
- Site access and slope. A flat lot with a wide side yard is straightforward. A sloped lot, or one where machinery cannot reach the build area, changes the foundation and the labour.
- Foundation type, which follows from the slope and the soil.
- Level of finish. An ADU built as a rental and one built for a family member to live in permanently are specified differently, and should be.
We work through all of these during the feasibility stage, before you spend anything on design. That is the point of doing feasibility first. You find out what your lot costs to build on while it is still a conversation rather than a set of drawings.
Our Process
- Consultation. We visit the property and talk through what the space needs to do.
- Feasibility and lot analysis. Setbacks, utilities, access, slope and existing structures. This is where we establish what your lot will actually support, before anyone pays for drawings.
- Design and engineering. Architectural design, structural engineering and 3D renderings.
- Permits. Submission and follow-through with the City of San Diego or County, handled by us.
- Construction. Foundation, framing, systems, inspections and finishes.
- Final inspection and occupancy. We see it through sign-off, then walk it with you.
What It Costs at a Glance
- Junior ADU (up to 500 sq ft): from $50,000
- Garage conversion: from $80,000
- Attached ADU: from $150,000
- Detached ADU: from $250,000
- Home additions: from $250 per square foot
- Ground-up construction: from $300 per square foot
Every project is scoped and quoted individually. City permits and fees are billed separately.
Financing
ADUs and additions are the largest projects most homeowners commission. We offer three financing routes:
- Enhancify, our online financing partner, linked directly from our site.
- Acorn Finance, built into our estimates.
- QuickBooks payment plans, arranged directly with us.
Additions and ADUs FAQ
How big can my ADU be?
It depends on your lot, your setbacks and the existing structures on the property. The limits are not the same for every parcel. We establish exactly what your lot supports during the feasibility review, before you commit to a design.
Garage conversion or a new detached build?
A garage conversion is usually faster and less expensive, because the structure and slab are already there. A new detached build gives you full freedom over layout, orientation and privacy. We price both during feasibility so you are choosing with real numbers rather than assumptions.
Will an ADU raise my property taxes?
Generally only the newly added value is assessed; your existing home is not re-valued from scratch. Confirm the specifics with a tax professional for your situation.
Can I rent out my ADU?
Long-term rental is the standard use, and it is the reason many of our clients build. Short-term rental is regulated separately in San Diego and the rules differ by area, and we will point you to what applies to your property.
How long does an ADU take?
Typically 10 to 14 months from first consultation to occupancy, including design, engineering and permitting. Construction itself is a portion of that. We give you a written schedule with the permitting stage shown separately, so you can see what is in our hands and what is in the jurisdiction’s.
Do I need an architect before I call you?
No. We are a design-build contractor, so design, engineering and construction all sit with one team under one contract. If you already have plans, we will build from them after a constructability review.
What warranty do you offer?
We stand behind our work per California CSLB standards: 4 years on workmanship and 10 years on structural.
Additions and ADUs Across San Diego County
Book a free consultation. We will walk the property, talk through what is possible on your lot, and give you a written scope and price.